Altered metabolism w/ barbiturates, rifampicin, antiepileptic drugs (eg, barbexaclone, carbamazepine, phenytoin, primidone), oxcarbazepine, topiramate, felbamate, griseofulvin, products containing St. John's wort (Hypericum perforatum
); HIV PIs (eg, ritonavir), NNRTIs (eg, nevirapine). Increased plasma & tissue conc of cyclosporin. Decreased plasma & tissue conc of lamotrigine. Reduced levels w/ antibiotics (eg, penicillins & tetracyclines). Requirement for antidiabetics may change.